High-Load Borage Oil Nanoemulsion Development via Polyol-Free D‑Phase Emulsification

This study presents the development of borage oil nanoemulsions using the D-phase emulsification (DPE) method, notably excluding alkyl polyols. Utilizing polysorbate 80 as the surfactant, the method achieves high oil concentrations (up to 50% w/w) with minimal surfactant use, obviating the need for hydrophilic-lipophilic balance adjustments. A Box-Behnken design analyzed the effects of borage oil, surfactant, and initial water concentrations on particle size and stability. Initial water concentration significantly reduced the average hydrodynamic diameter (AHD), with optimized formulations showing spherical droplets of 300-400 nm, narrow size distributions (PdI < 0.3), and robust zeta potential (←20 mV), maintaining physical stability for 12 months. Microscopy, X-ray diffraction, and thermal analyses affirmed the amorphous or liquid crystalline state of the formulations. Scale-up to 1 kg retained similar physicochemical properties. The in vivo toxicity assessment in the Galleria mellonella model indicated no significant toxicity, highlighting the formulation's safety. This scalable, solvent-free approach offers insights into the influence of key formulation variables, potentially advancing its application in pharmaceuticals.